3
Taste and Flavor Roles of Sodium in Foods: A Unique Challenge to Reducing Sodium Intake

From a culinary perspective, salt has many desirable properties. Added salt improves the sensory properties of virtually every food that humans consume, and it is cheap. There are many reasons for adding salt to foods. The main reason is that, in many cases, added salt enhances the positive sensory attributes of foods, even some otherwise unpalatable foods; it makes them “taste” better. For people who are accustomed to high levels of salt in their food, its abrupt absence can make foods “taste” bad. If we are to successfully lower salt consumption in the population as a whole, it will be necessary to reduce salt levels in the human food supply with careful attention to their flavor-enhancing properties. Consideration of what is known about the effects of salt on food and flavor perception and why people like foods with added salt can help to inform efforts to lower salt consumption. Further, knowledge of how salt is detected by sensory receptors may aid in developing salt substitutes or enhancers that could contribute to an overall reduction of salt in the food supply.

SALT THROUGH ANCIENT TIMES

It is first important to set salt consumption in historical context. Adding salt to food is a specific human trait (although Kawai [1965] wrote about an apparently learned behavior of Japanese macaques that involved dipping potatoes in salt water rather than fresh water, presumably to improve the flavor). It is believed that the relatively high salt usage of virtually all

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3
Taste and Flavor Roles of Sodium
in Foods: A Unique Challenge
to Reducing Sodium Intake
F
rom a culinary perspective, salt has many desirable properties. Added
salt improves the sensory properties of virtually every food that hu-
mans consume, and it is cheap. There are many reasons for adding
salt to foods. The main reason is that, in many cases, added salt enhances
the positive sensory attributes of foods, even some otherwise unpalatable
foods; it makes them “taste” better. For people who are accustomed to
high levels of salt in their food, its abrupt absence can make foods “taste”
bad. If we are to successfully lower salt consumption in the population as
a whole, it will be necessary to reduce salt levels in the human food supply
with careful attention to their flavor-enhancing properties. Consideration of
what is known about the effects of salt on food and flavor perception and
why people like foods with added salt can help to inform efforts to lower
salt consumption. Further, knowledge of how salt is detected by sensory
receptors may aid in developing salt substitutes or enhancers that could
contribute to an overall reduction of salt in the food supply.
SALT THROUGH ANCIENT TIMES
It is first important to set salt consumption in historical context. Adding
salt to food is a specific human trait (although Kawai [1965] wrote about
an apparently learned behavior of Japanese macaques that involved dip-
ping potatoes in salt water rather than fresh water, presumably to improve
the flavor). It is believed that the relatively high salt usage of virtually all

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STRATEGIES TO REDUCE SODIUM INTAKE
societies today became common beginning between 5,000–10,000 years
ago (He and MacGregor, 2007; MacGregor and de Wardener, 1998; Man,
2007). Most commentators believe that the reason for early salt use was
food preservation (MacGregor and de Wardener, 1998; Multhauf, 1978)
and that this early use was the origin of the current high consumption.
Nevertheless, with the advent of extensive salt mining and improved trans-
portation beginning in China more than 4,000 years ago (Adshead, 1992),
the characteristic taste of salted food became widely expected and accepted
(Multhauf, 1978). Indeed, it has been argued that many distinguishing char-
acteristics of human society and culture owe their origins to the desire for
salt and the salt trade (Beauchamp, 1987; Bloch, 1963; Fregley, 1980).
It is difficult to know how much salt was consumed by humans prior
to recent times, since the only good way to estimate intake is to determine
24-hour urinary excretion (for the most part, excess salt is not stored in
the body; therefore salt balance under most normal conditions is reflected
by equal input and output). Nevertheless, estimates based on historical
records have been made. In an estimate of early usage, the average daily
sodium intake in certain parts of China in 300 B.C. was reported to be
nearly 3,000 mg/d for women and 5,000 mg/d for men (Adshead, 1992).
Multhauf (1978) estimated that, in France and Britain in 1850, the human
culinary intake of sodium was 4,000–5,000 mg/d. These numbers, if reli-
able, are within the range of the amounts consumed in many societies today
(INTERSALT Cooperative Research Group, 1988). Thus, high salt intake
by humans does not have its origins in twentieth-century food processing,
but instead likely reflects food processing needs, especially preservation of
food, that originated thousands of years ago. It should also be acknowl-
edged that similarities in intake over time and across many different ethnic
groups have led to speculation that there may be some as-yet-unknown
physiological or nutritional factor that predisposes humans to desire a high
salt intake (Fessler, 2003; Kaunitz, 1956; McCarron et al., 2009; Michell,
1978), but there is little experimental support for this hypothesis (Luft,
2009), and some limited data are inconsistent with it (Beauchamp et al.,
1987). Further experimental evaluation about whether human sodium in-
take at levels far above any known physiological need is under metabolic
regulation will be of interest.
TASTE VERSUS FLAVOR
Taste and flavor are terms that are often confused. The word “taste”
has two meanings, one technical and the other as commonly used in the
English language, which encompasses the larger concept of flavor. In this
chapter, the word taste is used in its technical sense, but in other chapters
of this document, it is often used in its more generic sense.

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
Taste as a Technical Term
The sense of taste, one of the five major senses, is defined based on
anatomy. In mammals, it is the sense subserved by taste receptor cells lo-
cated primarily on taste buds in the oral cavity. These taste receptor cells
are innervated by branches of the seventh, ninth, and tenth cranial nerves
that synapse first in the brainstem prior to sending messages to other parts
of the brain (Breslin and Spector, 2008).
Most investigators agree that the sense of taste is composed of a small
number of primary or basic taste qualities, usually consisting of sweet, sour,
salty, bitter, and savory or umami (Bachmanov and Beauchamp, 2007). It
is thought that these specific classes or categories of taste evolved to help
the animal solve two of its most primary problems: the identification and
ingestion of nutrients and the avoidance of poisons. As a presumed conse-
quence of these dedicated critical functions, positive or negative responses
to taste compounds (tastants) are often genetically programmed. For ex-
ample, sweet tastants are generally innately liked and ingested by animals
that consume plants (herbivores and omnivores—some carnivores, such as
cats, do not detect sweet compounds) (Li et al., 2005). In contrast, bitter
tastants are generally disliked and avoided, since many are toxic (Breslin
and Spector, 2008).
Common Use of the Word Taste as a Synonym for Flavor
Virtually all foods and beverages impart sensations in addition to taste.
For example, a complex food such as soup not only has taste properties
(e.g., it is salty, sour, or sweet) but also has volatile compounds that give
it its specific identity (e.g., pea soup compared to potato soup), and it may
also have burning properties, such as those caused by hot peppers. These
sensory properties are conveyed by the sense of smell (cranial nerve 1), ex-
perienced mainly through the retronasal route—from the throat up through
the nasal passages and up to the olfactory receptors in the upper regions
of the nasal cavity—and the sense of chemesthesis (Green et al., 1990) or
irritation (cranial nerve 5), respectively. In common parlance, the entire
sensation elicited by this food is called its “taste.” However, most scientists
would instead use the term “flavor” to refer to this total sensation, and that
is how it will be used here. It should be noted that many also include the
texture of a food as a component of flavor. Taste molecules such as salt can
influence flavor in many ways, some of which are described below.
Importance of Flavor in Food Acceptance
Although this chapter focuses on how the taste imparted by salt influ-
ences food palatability, it needs to be emphasized that the other chemi-

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0 STRATEGIES TO REDUCE SODIUM INTAKE
cal sensory systems (smell, chemesthesis) that contribute to overall flavor
perception play a crucial role in food acceptance and thus may be useful
to take into account in developing strategies to successfully reduce overall
sodium in the diet (Koza et al., 2005). For example, certain volatiles de-
tected by smell receptors are often judged as “sweet” and may contribute
to judgments of a substance’s overall taste of sweetness and acceptability
(Schifferstein and Verlegh, 1996). An analogous phenomenon may also oc-
cur for saltiness (e.g., Manabe et al., 2009). Recent studies imaging the hu-
man brain (e.g., using functional magnetic resonance imaging) have shown
that flavor information from these separate sensory systems comes together
in several parts of the brain, most prominently in the orbitofrontal cortex
(Rolls et al., 2010). This leads to a unitary percept of flavor despite its be-
ing made up of anatomically independent sensory systems and emphasizes
the prominent role that overall flavor perception plays in judgments of a
food’s pleasantness.
More broadly, the addition of certain ingredients with high flavor im-
pact to the cooking or manufacturing process may assist in reducing the
need for added salt. For example, the addition of fresh herbs and spices,
citrus, mustards, and vinegars that impart distinctive flavorings may some-
times be used instead of or in conjunction with added salt, as has been sug-
gested by many authors writing about strategies for lowering sodium in the
diet (e.g., Beard, 2004; MacGregor and de Wardener, 1998; Ram, 2008).
Some cooking techniques (e.g., searing) may also help reduce the need for
added salt in many foodservice operations and in home cooking, in part
because they result in the production of new flavors (Ram, 2008). Whether
these techniques are applicable to foods prepared by manufacturers and
large foodservice operators requires study. Many foods prepared by manu-
facturers and in foodservice operations are necessarily highly processed;
they are cooked at high temperatures for relatively long periods of time,
and they must remain acceptable for extended periods. These contingencies
may work against using certain flavoring techniques and fresh ingredients
to reduce salt in some parts of the food supply. Further work to find alter-
native approaches is required.
Beyond the consideration of optimal sodium levels in a single manu-
factured food product, flavor issues need to be considered when evaluating
the palatability of sodium levels in composite dishes, whole meals, and
entire diets. The food supply contains a vast array of commercially success-
ful products and ingredients—fresh, prepared, and manufactured—whose
sodium levels range from very high to moderate to very low. The fact that
the same individual, for example, might be fully satisfied with two snacks
of widely varying sodium levels—one a fresh apple and the other a handful
of salted pretzels—reminds us how dependent the sodium taste issue is on
wider flavor contexts. The opportunities to successfully combine higher-

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
sodium foods with other foods that are naturally low in sodium (e.g., fresh
fruits and vegetables) in dishes or meals in ways that meet consumer taste
demands suggest a set of flavor questions that have not been adequately
studied. However, at least for foodservice and home cooking—if to a lesser
extent for food manufacturing—the salt taste challenge might be as much a
matter of reconsidering flavor options in recipe selection and menu develop-
ment (e.g., less aggregation of high-sodium ingredients in a single dish) as
needing to overcome technical challenges with salt substitutions.
SALT TASTE: HUMAN PERCEPTION AND PREFERENCE
Tastes have several sensory attributes that can be distinguished (Breslin
and Spector, 2008). Each molecule detected by the sense of taste is char-
acterized by one or more qualities—for example, salty, sweet, and bitter.
Sodium chloride, the prototypical salt taste molecule, imparts an almost
pure salt taste, whereas potassium chloride, often used in lowered-sodium
formulations, tastes both salty and bitter (this bitterness is one reason it is
often not fully successful in replacing the sensory effects of salt).
In addition to their qualities, taste molecules impart intensity: as con-
centration is increased, the saltiness also increases, up to some maximum
above which no further saltiness is perceived. Tastants also can be evaluated
for their time course or persistence. In the case of salt, taste intensity in-
creases within a few hundred milliseconds and then rapidly falls. This very
sharp time course is generally valued by the consumer. Tastes can also be
localized in the oral cavity. Salt taste can be identified by receptors through-
out the oral cavity, although there is evidence that the front and sides of the
tongue are more sensitive than the back (Collings, 1974).
A critical attribute of salt taste is its hedonic or pleasantness dimension.
For many foods, adding salt increases the liking for that food up to a certain
point, after which more salt reduces its pleasantness (palatability). This
inverted “U” function of added salt can be used in formulating foods, by
testing the acceptance of different salt concentrations with many consumers.
For any one food, there are substantial individual differences in where the
optimal point (which has been termed the “bliss point”) resides (McBride,
1994). Some of these differences are most likely due to differences in ex-
perience with salt in that food and other foods. That is, the optimal level
(the bliss point) can be shifted by altering one’s salt exposure. As described
later in this chapter, this theory provides a sensory basis for the committee’s
recommendations. Additionally, the term “bliss point” seems to imply that
the optimal level is a very precise point, when in fact there may be a fairly
wide range of concentrations of added salt that are judged fully acceptable.
For this reason, there may be a wide range of sodium levels within seem-
ingly similar food categories (Figure 3-1). Moreover, this phenomenon may

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STRATEGIES TO REDUCE SODIUM INTAKE
25
20
15
Acceptability
Sharp Optimum
(Food A)
10
Broad Optimum
(Food B )
5
0
0 2 4 6 8
Salt Concentration
FIGURE 3-1 Hypothetical analysis of optimal salt levels in two foods, A and B.
For food A, with a sharp optimum, it may be difficult to reduce salt levels quickly
if it is now manufactured or served -at eps
Figure 3 1. concentration level 4. For food B, if it is cur-
rently manufactured or sold at level 4, it may be relatively easy to reduce it to level
3, since this is equally acceptable.
help to explain why it is relatively easy in some instances to substantially
reduce salt in foods without reducing perceived pleasantness.
SALT FLAVOR EFFECTS
Salt imparts more than just a salt taste to overall food flavor. In work
with a variety of foods (soups, rice, eggs, and potato chips), salt was
found to improve the perception of product thickness, enhance sweetness,
mask metallic or chemical off-notes, and round out overall flavor while
improving flavor intensity (Gillette, 1985). These effects are illustrated in
Figure 3-2, using soup as an example. In the figure, the distance of each of
the points (e.g., “thickness,” “saltiness”) from the center point represents
the intensity of that particular attribute. This figure shows that when salt is
added to a soup, not only does it increase the saltiness of that soup (com-
pare closed circles with open triangles and open circles for saltiness), but
it also increases other positive attributes, such as thickness, fullness, and
overall balance.

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
FIGURE 3-2 Aroma and flavor profiles for split pea soup with 0.3 percent salt, 0.3
percent potassium glutamate, or nothing added.
SOURCE: Gillette, 1985. Reprinted with permission.
Figure 3-2
The mechanisms underlying these varied sensory effects of salt in foods
Bitmapped
are not well understood. In particular, how salt increases the perceived body
or thickness of liquids such as soups is a mystery. It is conceivable that in
addition to interacting with salt taste receptor(s), salt could also activate
somatosensory (touch) neural systems.
One understood mechanism by which sodium-containing compounds
may improve overall flavor is by the suppression of bitter tastes. Various
sodium-containing ingredients have been known to reduce the bitterness of
certain compounds found in foods, including quinine hydrochloride, caf-
feine, magnesium sulfate, and potassium chloride (Breslin and Beauchamp,
1995). Further, the suppression of bitter compounds may enhance the taste
attributes of other food components. For example, the addition of sodium
acetate (which is only mildly salty itself) to mixtures of sugar and the bit-
ter compound urea enhanced the perceived sweetness of this mixture as a
consequence of sodium suppressing bitterness and thereby releasing sweet-
ness, as illustrated in Figure 3-3. No change in sweetness was found when

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STRATEGIES TO REDUCE SODIUM INTAKE
18
16
Sweet
Bitter
Magnitude of Bitter or Sweet Taste
14
12
10
8
6
4
2
0
Mixture of 0.5 M Sucrose Mixture of 0.5 M Sucrose + 1.0 M Urea
+ 1.0 M Urea + 0.3 M Sodium Acetate
FIGURE 3-3 Magnitude of bitter or sweet taste of various solution mixtures. Add-
ing sodium acetate to a mixture of sucrose and urea increases the sweet, sucrose
taste while decreasing the bitter urea taste.
Figure 3-3.eps
NOTE: M = molarity of solution.
SOURCE: Breslin and Beauchamp, 1997. Adapted by permission from Macmillan
Publishers Ltd: Nature 387(6633):563, copyright 1997.
sodium acetate was added to sugar solutions without urea, indicating that
it is the suppression of bitterness by sodium acetate that is responsible for
the improved taste of those solutions (Breslin and Beauchamp, 1997).
Influence on water activity (the amount of unbound water) is another
proposed reason that salt may potentiate flavors in foods. Use of salt de-
creases water activity, which can lead to an effective increase in the concen-
tration of flavors and improve the volatility of flavor components (Delahunty
and Piggott, 1995; Hutton, 2002). Higher volatility of flavor components
improves the aroma of food and contributes greatly to flavor.
In short, salt plays a role in enhancing the palatability of food flavor
beyond imparting a desirable salt taste. This non-salty sensory role may be
magnified in products that have reduced amounts of other positive sensory
properties (e.g., low-fat products) or increased amounts of non-preferred
flavors (e.g., foods fortified with often bitter antioxidants). Consequently, in
reducing salt in the food supply, it may often be necessary to identify ways
to replace the flavor-modifying effects of salt. This illustrates the technologi-
cal challenges that have to be met in successfully reducing salt in complex
foods while maintaining their palatability. Further research is needed to
understand all of the perceptual attributes of salt in foods.

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
MECHANISMS OF SALT TASTE
Sodium chloride—once dissociated into ions (individual atoms that
carry an electrical charge)—imparts salt taste. It is now widely accepted
that it is the sodium ion (Na+) that is primarily responsible for saltiness,
although the chloride ion (Cl−) plays a modulatory role (Bartoshuk, 1980).
For example, as the negatively charged ion (anion) increases in size (e.g.,
from chloride to acetate or gluconate), the saltiness declines. Many sodium
compounds are not only salty but also bitter; with some anions, the bitter-
ness predominates to such a degree that all saltiness disappears (Murphy
et al., 1981).
It is believed that there are two or more types of receptors in the oral
cavity, primarily on the tongue, that are responsible for triggering salt tastes
(Bachmanov and Beauchamp, 2007), but major gaps in the understanding
of salt taste reception remain. The most prominent hypothesis, which has
been demonstrated in mice and rats, is that one set of receptors playing a
role in salt taste perception involves ion channels or pores (Epithelial so-
dium [Na] Channels: ENaCs). ENaCs allow primarily sodium (and lithium)
to move from outside the taste receptor cell, where it has been dissolved
in saliva, into the taste cell. The resulting increase in Na+ inside the taste
cell causes the release of neurotransmitters that eventually signal salt taste
to the brain (Chandrashekar et al., 2010; McCaughey, 2007; McCaughey
and Scott, 1998) (Figure 3-4). Because sodium and lithium are the only
ions known to produce a purely salt taste, it is believed that these sodium-
and lithium-specific channel receptors play a major role in sensing saltiness
(Beauchamp and Stein, 2008; McCaughey, 2007).
The body of evidence supporting sodium channel receptors as salt taste
receptors is based largely on animal models, primarily rodents. These find-
ings indicate that the diuretic compound amiloride, a molecule that blocks
sodium channels, reduces salt taste perception in these animals. In humans,
however, amiloride is much less effective in blocking salt taste perception
(Halpern, 1998). Nevertheless, since human salt taste mechanisms are
highly unlikely to differ in fundamental ways from those of rodents, most
investigators are convinced that an ENaC is the most likely receptor in
humans as well. If this hypothesis is correct, it has profound implications
for the search for salt substitutes. Given the specificity of this channel for
sodium, it is highly unlikely that any substance could fully replace sodium
(with the exception of lithium, which is unacceptable because it is highly
toxic).
At least one other type of taste receptor that detects sodium chloride
and some other salts is thought to exist. The hypothesis for a second re-
ceptor is based in part on work showing that some salt taste is perceived
even when cations that cannot fit into the ENaC (potassium, calcium, am-

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STRATEGIES TO REDUCE SODIUM INTAKE
Na+
Oral Cavity
α, β, γ Li pid Bilayer
Protein Unit s
Interi or of
Na+ Release of Neurotransmitters
Taste Re cept or Ce ll
FIGURE 3-4 An epithelial sodium channel (ENaC). The epithelium is represented
as a lipid (fat) bilayer (round circles), the area above the lipid bilayer (oral cavity)
represents the outside of the taste receptor cell, and the area below the lipid bilayer
is the interior of the taste receptor cell. The channel itself is made up of three protein
units (alpha, beta, and gamma) that are represented by the cylindrical structures.
Figure 3−4
This channel is thought to form a tunnel through the taste receptor cell that allows
Na+ ions outside the cell to move inside the cell. This channel is quite specific to
sodium, which may explain why few compounds are purely salty. Once sodium is
inside the taste receptor cell it causes a cascade of biochemical reactions that result
in the release of neurotransmitters that signal salt taste to the brain.
monium) are present, rather than sodium or lithium. In addition, salt still
elicits a taste in animal model studies, although to a lesser extent and with
less specificity, when the ENaC is blocked by amiloride (DeSimone and
Lyall, 2006; McCaughey, 2007). A full understanding of how salt taste is
recognized by humans, a major gap in our understanding, could facilitate
the discovery of effective and economically feasible salt taste enhancers.
EVOLUTION OF SALT TASTE PERCEPTION AND PREFERENCE
It is widely assumed that the ability to detect salt—hence, salt taste
perception—arose in response to the need by plant-eating organisms to
ensure an adequate intake of sodium (Denton, 1982; Geerling and Loewy,
2008). Sodium is crucial to many physiological processes, and the body
cannot store large amounts. Moreover, outside the sea, salt is often hard to
find or in low levels in the environment (Bloch, 1963).

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
There are two conditions under which animals, including humans,
choose to consume salt. The first, which has been widely studied in ex-
perimental animals, occurs when there is a true sodium need, such as
experienced by many plant-eating animals that live in low-sodium envi-
ronments. This is called salt need (Denton, 1982; Geerling and Loewy,
2008). A number of hormonal, central nervous, and behavioral systems
are engaged when an animal is truly deficient in sodium, which motivates
it to search for sodium salts, avidly consume them based on their salt taste,
and thereby restore sodium balance (Morris et al., 2008). Sodium-depleted
animals have an innate ability to recognize, by its distinct taste, the needed
nutrient. Although true sodium need may be experienced by humans under
some conditions and has been studied experimentally (Beauchamp et al.,
1990; McCance, 1936), it is a very rare occurrence under most circum-
stances. It thus cannot explain why humans consume as much salt as they
do (Beauchamp and Stein, 2008; Leshem, 2009). A marginal deficiency of
other minerals, particularly calcium, may play a role in stimulating human
salt intake (Tordoff, 1992). If this proposed relationship is supported in
further studies, it would suggest that one strategy to reduce salt liking and
perhaps intake would be to encourage increased calcium consumption,
which is already strongly recommended for bone health (HHS, 2000).
The second condition responsible for salt intake occurs in many species,
including humans, even when there is no apparent need for salt—that is,
when sufficient sodium for all bodily needs has been consumed. This has
been termed salt preference (Denton, 1982), even though the desire does
not reflect a conscious preference. Taste preference for salt (in the absence
of need) has been identified in many animals. Humans generally consume
far more salt than is actually necessary and continue to enjoy salty foods
even when physiological needs are met. Thus, it appears that salt preference
rather than a true physiological need drives salt intake in human popula-
tions. Why people consume so much more salt than they need is a concept
that is not fully understood and needs explanation.
It has been argued that a preference for salt beyond physiological need
is due primarily or exclusively to learning, particularly early learning, or
even that it is an addiction (Dahl, 1972; MacGregor and de Wardener,
1998; Multhauf, 1978). In contrast, other investigators have argued that
while learning may play a role, evolutionary pressures to consume salt
have shaped people and some other animals to have an innate liking for its
taste, even when sodium is not needed (Beauchamp, 1991; Denton, 1982).
Denton (1982) noted that merely because salt is consumed in excess of
contemporaneous need in no way mitigates against such consumption being
driven by innate propensities, just as sexual activity occurs in the absence
of intent to increase numbers of the species. Even under the first hypoth-
esis, which proposes that high salt intake is due to powerful learning, salt

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0 STRATEGIES TO REDUCE SODIUM INTAKE
a diet with a 30–50 percent overall reduction in sodium content for 2 to 3
months, volunteers gradually developed a preference for foods with lower
salt levels. In other words, they acclimated to the lower-salt diet. In a study
with many more subjects, Elmer (1988) reported very similar results, as
shown in Figure 3-5.
This shift in preference may also be moved in the other direction: when
people were placed on a higher-salt diet, they shifted preference upward to
like more salt in their foods (Bertino et al., 1986). A number of lines of
evidence suggest that these shifts are due to the actual sensory experience
with salt rather than some sort of physiological regulatory process (Leshem,
2009).
Most of the research on the sensory effects of lowering sodium intake
was conducted more than 20 years ago, and many important questions
were never fully explored. For example, it is not known whether it is nec-
essary to reduce total sodium intake to obtain sensory accommodation or
whether it would occur if salt were reduced in a single product category,
such as soup or bread. That is, would the consumer begin to prefer lower-
sodium soup or bread if his or her overall sodium intake was not reduced at
the same time? Also, would judicious consumption of very salty food items
(e.g., olives, anchovies, certain cheeses, processed meats) in the context of
an overall lower-salt diet inhibit these sensory changes? Furthermore, it is
also not known how long such sensory changes persist or how resistant they
10
||
0
Change from Baseline (%)
Change in
{ Sodium Excretion
Control
Change in
–10
O ptimal Sodium
Change in
{
Low Sodium Sodium Excretion
–20
Change in
O ptimal Sodium
||
–3 0
Baseline 6 12 18 24 48 54
Weeks on Low Sodium Diet
FIGURE 3-5 Shifting of salt taste preference in response to a lower-salt diet. Change
in salt content of the diet indicated by the change in urinary sodium excretion.
SOURCE: Elmer, 1988.
Figure 3-5.eps

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
would be to shifts back upward when an individual temporarily goes off
the low-sodium diet. Finally, and perhaps most importantly, this mechanism
of decreasing the desire for salt has not been tested in young children for
whom, based on the arguments above, it might be particularly effective in
reducing this desire. In this regard, it might have been expected that the
elimination of added salt in virtually all commercially prepared baby food,
which occurred more than 30 years ago (Barness et al., 1981), would have
reduced salt preference in children. Unfortunately, there are no data avail-
able by which this hypothesis could be tested. And because many parents
use table foods during weaning, the sensory effects of elimination of added
salt to baby foods may not be easy to detect even if appropriate data were
collected.
Despite these outstanding questions, it seems likely that if salt intake
from foods could be reduced on a population-wide basis, consumers’ pref-
erence for salty foods would also shift downward. It will be critical to
monitor this proposed shift in preference along with monitoring changes in
overall consumption in any nationwide salt reduction program.
Potential Sensory Approaches for Successful
Reduction of Salt in the Food Supply
Gradual Reduction Without Consumers’ Knowledge
One approach to changing ingredients in foods without the consumer
noticing is to make the change gradually (Dubow and Childs, 1998). Per-
ceptual studies with taste show that people are generally unable to detect
differences between two concentrations of a taste substance when the
difference is less than approximately 10 percent (called a Just Noticeable
Difference [JND]; Pfaffmann et al., 1971). However, it may be the case that
this estimate is misleading because it is based on sensory tests with pure
taste solutions, not real foods. Foods are much more chemically complex
and this complexity could make it more difficult to identify changes in
individual ingredients. For example, M. Gillette1 has suggested that the
JND in foods is more likely 20 percent and thus a change of 15 percent
would not be noticed. However, a representative at the committee’s public
information-gathering workshop (March 30, 2009) reported the opposite
in some cases. Reductions in sodium content well below 10 percent in some
food systems resulted in significant loss of palatability, indicating that these
small changes could be perceived. A possible explanation for this is that,
as discussed above, the other sensory actions of salt may be characterized
by smaller JNDs. Apparently, for each food, this is an empirical question
1 Personal communication, M. Gillette, McCormick & Co. Inc., January 2010.

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STRATEGIES TO REDUCE SODIUM INTAKE
that will require data to determine the size of a detectable salt reduction.
More research in salt-flavor interactions may, however, reveal general prin-
ciples that will permit predictions in different food systems. Based on this
reasoning, it has been suggested that a gradual reduction of salt in food, in
incremental steps, would be unnoticed by the consumer. According to this
argument, if incremental reductions were instituted regularly (e.g., once
each year or even more frequently), it would be possible to substantially
reduce the salt content of foods over the course of several years without
the consumer noticing. For example, Girgis et al. (2003) reported that 25
percent of the salt in bread could be eliminated, over a cumulative series
of small decreases, without people recognizing a taste change (see also,
Cauvain, 2007). All sellers of bread would have to make this reduction;
otherwise, the changes would be noticed, and the reduced sodium version
would be less preferred.
This is an attractive strategy for reducing salt in foods while main-
taining their acceptability, and several food manufacturers are reported
to have already undertaken it. However, advancements in several research
areas may optimize the implementation of such a strategy. First, industry
has not undertaken reduction of sodium across all foods, so there may be
some individual products for which reductions may be limited. Second,
it is likely that there will be a limit to reductions that can be achieved by
simply lowering sodium content without additional reformulation and taste
changes, but there are no published data testing the limits of this strategy.
It seems likely for many foods that at some point further reductions may
not be possible while maintaining consumer palatability. Determination of
where the point of limited reductions resides will vary by food item and is
a focus of industry research during the reformation process. Third, since
salt has many sensory functions in foods in addition to making it taste salty,
it is unclear whether changes in these other functions would go unnoticed
following small reductions or whether additional changes in food formula-
tions would be required.
Use of Low-Sodium Foods and Ad Libitum Salt Use
Reduction of sodium intake may be achieved by reducing salt in food
and permitting people to use a salt shaker to add back to the food as
much salt as desired (i.e., ad libitum salt use). For example, in one study
(Figure 3-6), sodium intake from clinically prepared foods decreased from
an average of 3,100 mg/d to an average of 1,600 mg/d over a 13-week
period, and participants were permitted unlimited use of a salt shaker to
salt their food to taste. Importantly, less than 20 percent of the overall
sodium removed during food preparation was replaced by increased use of
table salt—the use of which was measured without participants’ knowledge
(Beauchamp et al., 1987).

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STRATEGIES TO REDUCE SODIUM INTAKE
Use of Other Flaors or Flaoring Techniques to Reduce the Need for
Added Salt
It is possible to replace some of the salt in foods with other taste or
flavor compounds or through other flavor strategies or techniques. Some
of these compounds or strategic elements may be added by the processor,
chef, or consumer, whereas others may be created during food preparation,
such as cooking.
A prominent example of an added compound involves glutamic acid
(an amino acid). Combining glutamic acid with sodium creates the well-
known flavoring compound monosodium glutamate, or MSG. MSG im-
parts a savory taste (called “umami”) as well as a salt taste to food. Some
studies have shown that it is possible to maintain food palatability with a
lowered overall sodium level in a food when MSG is substituted for some of
the salt (Ball et al., 2002; Roininen et al., 1996; Yamaguchi, 1987). In these
cases, less MSG is added back to the food than is removed by using less salt.
Other possibilities for the use of glutamates are included in Appendix D,
Table D-2. It should be noted that although the use of MSG is controversial
(Fernstrom, 2007), it is a generally recognized as safe (GRAS) substance.2
Beyond MSG, quite a wide number of naturally occurring or traditionally
prepared foods exhibit these same “umami” qualities (e.g., mushrooms, to-
matoes, vegetable extracts) that might displace some of the need for added
sodium in food preparation or manufacturing (Marcus, 2005).
Potential Technological Approaches for
Reduction of Salt in the Food Supply
Modification of the Size and Structure of Salt Particles
For surface applications of salt to foods (e.g., on potato chips), chang-
ing the size of salt particles can make it possible to provide the same salt
taste with a lower amount of salt. Dissolution of salt in the mouth is needed
to impart a salt taste, but ordinary salt particles often do not dissolve com-
pletely. Changing the size of salt particles can help improve dissolution and
thereby increase the salt taste of the salt (Kilcast, 2007).
Changing the crystal structure of salt may also produce the same salt
taste from reduced amounts of salt in the product (Beeren, 2009). Ad-
ditional technologies being investigated to provide salt taste with less salt
include mock salts and multiple emulsions. Mock salts are starch particles
coated in a thin layer of salt. For topically applied salt applications, these
particles can create surface coverage with less salt (Kilcast, 2007).
2 21 CFR 182.1(a).

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TASTE AND FLAVOR ROLES OF SODIUM IN FOODS
Multiple emulsions are also being investigated as a way to maintain
salt taste in sodium- and fat-reduced emulsion products. These emulsions
consist of water droplets dispersed in fat droplets that are then dispersed
in another outer layer of water that contains salt. The inner layer of water
dispersed in the fat droplets can be sodium-free and can replace some of
the volume of the product, requiring less of the outer, salted aqueous phase
(Figure 3-7). As a result, consumers of these products will continue to
enjoy the salt taste of the outer aqueous phase while consuming less total
sodium.3
Use of Different Salt Sources: Sea Salt
It is possible that the crystal structure of sea salt may be responsible
for its pleasing taste profile when used on the surface of foods (Kilcast,
2007). Sea salt usually contains minerals in addition to sodium that impart
a variety of tastes that may be desirable in some cases, but may also impart
bitter aftertastes. While unsubstantiated reports from trade journals suggest
that sea salt may contain as little as 41 percent sodium chloride (Pszczola,
2007), sodium chloride is the main component of most sea salt and thus its
composition is similar to table salt.
Use of Substitutes and Enhancers
One approach to reducing salt in the food system would be the develop-
ment of salt substitutes with the same sensory properties as salt but without
the sodium—a sort of aspartame or sucralose but for salt. Alternatively, one
might develop a salt taste enhancer, a compound that magnifies the taste
of low levels of salt. Adequate substitutes and enhancers for many uses do
not yet exist, but one way to attempt to identify such molecules is to use
the salt taste receptor to assay for such effects. Unfortunately, the molecu-
lar and cellular mechanisms underlying salt taste perception are not fully
understood, and this represents a major gap in both our understanding and
our ability to efficiently search for salt substitutes and enhancers.
The hypothesized specificity of the salt taste mechanism makes the exis-
tence of a true salt taste substitute unlikely, although not impossible. Thus,
this differs in principle from a sweet taste, where the receptor mechanisms
are more easily mimicked by other molecules; as a consequence, there exist
many alternative sweeteners (Beauchamp and Stein, 2008). Many of the
alternative sweeteners now used were discovered serendipitously, but no
non-sodium, primarily salty-tasting molecule has ever been identified, with
perhaps the single exception of potassium chloride.
3 Personal communication, C. Bereen, Leatherhead Food International, March 30, 2009.

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STRATEGIES TO REDUCE SODIUM INTAKE
Sodium-free
Water Droplets
Oil/Fat
(Outer Phase of
Sodium-containing Water)
FIGURE 3-7 Multiple emulsion consisting of fat droplets dispersed in the outer
phase of sodium-containing water and other water-soluble components. To expand
the size of the fat droplets and create less need for the sodium-containing outer
phase, sodium-free water droplets are dispersed within the fat.
SOURCE: Adapted from Beeren,Figure 3-7.eps
2009.
Potassium chloride has been proposed as a salt substitute either alone or
in combination with table salt. However, in addition to tasting salty, many
people find potassium chloride bitter (Beauchamp and Stein, 2008). None-
theless, the interest in increasing potassium consumption among Americans
has resulted in considerable interest in pursuing potassium chloride as a salt
substitute. As shown in Appendix D, Table D-1, many foods use potassium
chloride mixed with sodium chloride in up to a 50:50 ratio; a significant in-
crease in bitterness is observed when a higher ratio is used (Desmond, 2006;
Gou et al., 1996). Other salt substitutes have been proposed, but most of
the claims remain scientifically unverified (see Appendix D, Table D-1).